The invention of this application relates to a coronary artery graft flow-meter. More particularly, this invention relates to a coronary artery graft flow-meter apparatus for insertion into a delivery line for solution to be perfused through grafts after the grafts have been anastomosed to coronary arteries.
Indirect flow-meters for coronary artery grafts have been notoriously unreliable and most open-heart surgery centers no longer use them. Direct flow-meters have the disadvantage of possible contamination and/or air embolization. Consequently, there has been a substantial need for a device which is able to overcome both of these possible sources of danger and which would provide a disposable, low-volume closed system that can be inserted into the delivery line for the cardioplegia solution or cold solution which is perfused through grafts after they have been anastomosed to the coronary arteries.
Various flow-rate sensing systems and auto-transfusion systems have been previously suggested. Abrams, U.S. Pat. No. 4,613,325, describes a flow-rate sensing device for use in regulating the rate of flow in a system for parenteral administration of liquids to patients. The liquid emerges from a storage reservoir and is fed into a housing through an upstream flow passage portion and is then made to pass through a narrow flow passage wherein the velocity of the liquid increases while its pressure decreases. The liquid then emerges into a downstream flow-through passage and flows through an outlet from the housing. A pressure transducer, consisting of two chambers separated by a resilient deformable diaphragm, has its upstream chamber in fluid pressure communication with the upstream flow path portion and its downstream chamber in fluid and pressure communication with the flow emerging from the throat passage. Variations of the flow rate through the throat passage effect changes in the pressure differential between the transducer chambers and thus cause variable degrees of displacement of the transducer diaphragm.
Bartlett, U.S. Pat. No. 4,547,186, describes a system for autotransfusion which has an aspirating wand or tube coupled to a vacuum source through a reservoir for receiving aspirated blood. Blood flows from the reservoir to a receiving bag in a relatively low position below the elevation of the patient. When there is sufficient blood supply in the bag, it is elevated from this lower position to a point higher than the patient. Blood then flows from the elevated bag by gravity through a conducting tube and a needle into the patient.
Schmid-Schonbein et al., U.S. Pat. No. 4,474,538, describes a method of circulating organo-biological fluids wherein a fluid contained in a reservoir is released to a pressure level lower than its original fluid pressure level. Thereafter, it is raised periodically to a pressure level above the original level, then transferred from such level to a reservoir position at a predetermined, relatively lower pressure level. It is then drained to an outlet position approximately at the level of the original pressure level.
Welch et al., U.S. Pat. No. 4,014,329, describes a method and device for autotransfusion of blood during surgery. Shed blood is retrieved from a surgical field via a receiving vessel located within a vacuum chamber and under less vacuum than the vacuum applied to the chamber. The vacuum and receiving vessel draw blood from the surgical field into the receiving vessel where it is first collected and then passed to a second vessel. The blood is transferred from the second vessel to the patient during reinfusion.
Rosenberg, U.S. Pat. No. 3,896,733, describes a continuous-flow two reservoir fluid or blood-feed system for administration of fluids to patients. The apparatus is composed of two reservoirs each filled by way of check valves from a common supply and having common connections to a vacuum line. Application of vacuum draws the fluid from the supply line into one of the reservoirs, while fluid is led from the other reservoir to the patient.
DeVries, U.S. Pat. No. 3,709,222, describes a method and apparatus for automatic peritoneal dialysis which includes a series of steps for the exchange of dialysate which proportions the in-flow to the out-flow and provides for the elimination of any distressing in-flow or out-flow pressures on the patient and any abnormal build-up of fluid quantity in the patient. The apparatus includes a portable bed-side unit which carries the necessary pumps and valves for the automatic cycle. It includes a disposable sheet unit supported on the apparatus which is positioned such that pumps and valves in the apparatus can operate on the unit when it is in place.
Gorsuch, U.S. Pat. No. 3,690,318, describes an apparatus which is mounted adjacent to a patient which supports an inspection chamber at a predetermined elevation with respect to the patient. The chamber is connected to the patient through an infusion supply tube. Intravenous infusion fluid is supplied from a container to the inspection chamber at a predetermined pressure and a selected rate. Fluid level sensors give warning if the fluid level in the inspection tube rises or falls a preselected amount.
Robicsek, U.S. Pat. No. 3,017,885, describes means for measuring the flow of blood through an artificial heart-lung pumping system. The means comprise a blood flow meter which is attached directly to a conduit through which blood flows from the heart-lung pump to the patient. It includes means for measuring the drop in fluid pressure as the blood flows through a constriction in the conduit. The pressure drop therein is said to be proportional to the rate of flow of the blood.
Buckberg et al., U.S. Defensive Publication No. T994,001, describes a delivery system for injecting a cardioplegic solution made up mostly of a patient's own blood into his or her heart in order to arrest it. The delivery system is used in combination with a cardiopulmonary by-pass apparatus. The delivery system includes a blood bag for storing a portion of the patient's blood, a Y-shaped tubing having a first end with a single opening and a second end with a pair of openings with the single end mechanically coupled to an oxygenator so that the blood will travel from the oxygenator to the Y-shaped tubing, and a heat exchanger disposed between the blood bag and one of the pairs of openings of the second end of the Y-shaped tubing and connected thereto so that blood may be pumped from the oxygenator through the heat exchanger into the blood bag by a first small roller pump.
Heretofore, none of the flow rate systems for coronary artery grafts provided reliable and safe measurements of the rate of flow through such grafts. The invention disclosed herein comprises a coronary artery graft flow-meter apparatus for insertion into a delivery line for solution to be perfused through a graft after the graft has been anastomosed to a coronary artery or arteries and which provides a measurement of the flow rate of the solution through the graft.